Treatment of acidic compositions



Patented Nov. 1, 1949 TREATMENT OF ACIDIC COMPOSITIONS Carl N. Zellner,New Provldente, N. 1., assignor to Tide Water Associated Oil Company,Bayonne, N. J., a corporation of Delaware No Drawing. Application August20, 1947, Serial No. 769,761

11 Claims. (Cl. 260-452) This invention relates to a method forrecovering or separating acids from complex organic mixtures. Moreparticularly, the invention is concerned with the treatment of complexacidic organic mixtures which may contain polyfunctional oxygenatedcompounds to improve the yield of acids recoverable therefrom.

The method of this invention has particular efiectiveness when appliedto the treatment of certain acidic compositions comprising, in intimatemixture, dibasic and monobasic acid substances of various molecularweights and other monoand di-functional organic compounds. It isespecially adaptable to the recovery of dibasic acids from the crudeoxidation product, or suitable fractions thereof, resulting from liquidphase oxidation of hydrocarbons with a free-oxygencontaining gas, as forexample, air, oxygen, and the like. Hence the present invention will bedescribed herein in illustrative embodiment in its application to thetreatment of such hydrocarbon oxidation products.

The crude hydrocarbon oxidation products embodied for treatment arehighly acidic and have a saponiflcation value of at least about 400mgms. KOH per gram, as for example, 500-625, and contain a substantialamount of dibasic acids and/ or certain potentially acid componentsconvertible to dibasic acids. Such desirable crude oxidationproducts maybe obtained by liquid phase oxidation of hydrocarbons to the extent offormation of dibasic acid constituents in preference to monobasic acids.Illustrative thereof are oxidized hydrocarbon products described, andprepared in the manner set forth, in my copending application Serial No.625,961, filed October 31, 1945. Hence, the crude oxidation products, asembodied for treatment herein, are distinguishable from the hydrocarbonoxidation products known to the art which have saponification valuesmaterially lower than about 400 mgms. KOH, and hence, contain no dibasicacids or, if any, not more than a trace of such acids or potentiallyacid constituents convertible to dibasic acids. Moreover, the

crude oxidation products, as embodied for treatment herein, are alsodistinguishable from the oxidation products resulting from nitric oxideand nitric acid oxidation of hydrocarbons in that the oxidation productsembodied herein are more heat sensitive and contain partially oxidizedintermediates that inhibit crystallization of dibasic acids presenttherein. Oxidation of hydrocarbons with nitric acid or nitrogen oxidesdestroys these intermediate partially oxidized materials and producesproducts that do not present the resiniflcation problems of the crudeoxidation products as embodied herein for recovery of high yields ofdibasic acids.

, tional groups indicates the presence of ester and lactonic linkages aswell as carboxyl groups. Relatively few free hydroxyl groups arecontained in these reactor products, and free aldehyde, ketone groupsand anhydrides appear to be virtually absent. Dibasic acids of thesuccinic acid series may be crystallized out only in limited amounts bysimple cooling of the crude oxidation product. Extraction of theoxidation product with water to separate water-insoluble andwater-soluble components often gives rise to troublesome emulsions.

It is desired to increase the acid yield, particularly dibasic acids,and improve the recovery of such acids from complex mixtures asdescribed hereinbefore. One suitable method for obtaining such improvedyields comprises subjecting the aforedescribed acidic mixtures to acontrolled or selective heat treatment.

Although improved results are obtained by the pyrolysis method, I havefound that still higher yields of dibasic acids are obtainable byemploying the method of the present invention, which, in broad aspect,comprises subjecting the acidic mixture to a controlled or selectivepyrolysis in the presence of a catalyst. The actual conditions employedin the method of this invention may vary somewhat, depending upon theparticular apparatus and type of charge material employed, and the exactresults desired, but in general, the selective catalytic pyrolysis is soregulated as to break down or convert certain potentially acidcomponents to free acids, raise the ratio of acid value tosaponification value, and to remove or decompose certaincrystallizationrinhibiting substances without causing substantial, ifany, decarboxylation of the desired dibasic acids. Essentially, this isbrought about in pyrolysis, in the presence of a catalyst, by suitablecontrol of the temperature and of the period of time at which thetemperatures employed, the shorter is the time required. Althoughtemperatures lower than about 200 C. and higher than about 400 C. may,under certain conditions be suitably employed,'I prefer, in my practiceof the invention to use temperatures in the range of about 200 to 400 C.Use of temperatures within this range have been found to provide highlysatisfactory results as embodied herein. Although temperatures higher orlower than the foregoing range may, under some circumstances beemployed, higher and lower temperatures are not generally preferred asexcessively high temperatures tend to increase material losses whereasuse of lower temperatures increase the reaction time. In a preferredembodiment, the charge is maintained at the desired reaction temperaturefor a relatively short period which may be only a matter of a fewseconds. For example, when using a temperature of about 200 to 400 0.highly satisfactory results may be obtained by maintaining stock beingsumcient to vaporize the charge in the flask almostimmediately, andallow a contact time (residence time) of about 3 seconds in the heatedzone. The overhead formed was condensed and collected in a receiver,followed by a dry ice trap to condense low boiling material, and adrying tube and ascarite tube to absorb water and carbon dioxiderespectively. Break up of the crude acidic mixture was as follows:

Percent by weight Overhead 55 Bottoms 31 Dry Ice trap contents 1 Water 4Carbon dioxide .1 Loss 8 the charge in contact with the catalyst forabout 0.5 to 5 seconds, the shorter contact times being employed at .thehigher temperatures. In my practice of the invention, I have found thatuse of a catalyst in the pyrolysis treatment not only markedly increasesthe yield of dibasic acids from the aforedescribed acidic mixtures, butalso f acilitates the separation, as by filtration, of the dibasic acidsfrom the thus-treated oxidized hydrocarbons.

The process of this invention, in practical embodiment, may involve acontinuous pyrolysis treatment in the presence of a catalyst in which astream of the charge material is conducted into a heated,catalyst-containing conversion zone and rapidly vaporized therein. Inthis manner, the desired conversion and the primary separation of theacidic mixture into an overhead or distillate fraction and residual orbottoms fraction are accomplished in one heating operation. Thetreatment of the present invention desirably is conducted underatmospheric or subatmospheric pressure, the latter being preferred inpermitting use of shorter contact time and thus decreasing any tendencyfor undesired decomposition to occur. Furthermore, the charge materialmay be treated with advantage in the presence of steam or an inert gas,e. g., nitrogen. As is apparent from the description herein of myinvention, various apparatus and procedures for conducting the pyrolysistreatment in the presence of a catalyst may be employed, andfurthermore, that operating conditions may vary somewhat with differenttypes of apparatus and the particular results desired.

In order to further describe my invention, the following illustrativeexamples are set forth showing the markedly improved yields of dibasicacids obtained by practicing the present invention.

Example I A refined paraifin wax of 120 F. melting point was subjectedto liquid phase oxidation with air under controlled conditions until theresidual oxidation product had a saponification value of 530 and an acidvalue of 336; that is, an acid/saponiflcation ratio of 0.63.

This crude oxidation product was subjected to a pyrolysis treatment,without use of a catalyst, by continuously adding the crude product at arate of three grams per minute to a heated flask maintained at 270-280C. under a vacuum of about 10 mm. A total of about 296 grams was thusadded, the rate of introduction of charge The overhead fraction wasdistilled into three fractions under a vacuum of 4 mm.,-after which eachfraction was filtered to obtain crude crystalline dibasic acids. Thecrude crystals were washed with two parts by weight of a 1:1 mixture ofheptane and benzene to remove oily non-crystalline material adhering tothe crude crystals. The three fractions had the properties as shown inthe following tabulation, and the amount of dibasic acids obtained fromeach fraction were as set forth. The acid, saponification, andacid/saponification values set forth are the values of the dibasic acidsyielded from each fraction.

Total 23.5

In the foregoing tabulation the acid and saponification values of thefractions were determined in water, and the substantially equivalentacid and saponification values in each fraction clearly shows that thefractions contained substantially pure acids.

After removal of the dibasic acids from the foregoing fractions, thefiltrates from the fractions were combined and redistilled. Anadditional 4.7 grams of dibasic acids was thus obtained. Hence, a totalyield of 28.2 grams of dibasic acids was obtained from the non-catalyticpyrolysis of the crude product, representing a yield of 9.5% of dibasicacids based on the charge.

Example II In a manner identical to the foregoing example, 217 grams ofthe same charge stock was subjected to a pyrolysis treatment underidentical conditions as in Example I, except that grams of a catalystwas present in the flask with which the vaporized product in thefiask'was in contact. The catalyst employed was a silicaalumina crackingcatalyst in the form of pellets.

Break up of the acidic mixture charged to the catalytic pyrolysistreatment was as follows:

Percent by weight Overhead 61 Acid value=465 Saponification value=592Acid to saponiilcation=0.78

Bottoms 14 Dry Ice trap contents Water 6 Carbon dioxide 4 Loss 10 Theoverhead was distilled into three fractions, and the crude crystalsobtained from filtration of each fraction were washed in exactly thesame manner as in Example I. The three fractions had the properties asshown in the following tabulation, and the amount of dibasic acidsobtained from each fraction was as set forth, the acid, sapom'fication,and acid/saponification values set forth being those of the dibasicacids yielded from each fraction.

Dibasic acid yield, grams Fraction I:

Boiling point 102-l59 C. at 6 mm.

pressure 9.4

After removal of the dibasic acids from the foregoing fractions, thefiltrates from the fractions were combined and redistilled. Anadditional yield of 6.3 grams of dibasic acids was obtained. Thus atotal yield of 28.9 grams of dibasic acids was obtained, representing ayield of 13.3% of dibasic acids from the hydrocarbon charge subjected tothe catalytic pyrolysis.

The foregoing results clearly show that by employing the catalyticpyrolysis method of the present invention, as compared to the sameprocess except that the cracking catalyst is not used, the yield ofdibasic acids from the same charge stock is materially increased. Forexample, in Example I, non-catalytic pyrolysis of the crude chargeyielded 9.5% of dibasic acids, whereas, under otherwise identicalconditions, the catalytic treatment of Example II yielded 13.3% ofdibasic acids. In other words, by use of the process of thepresentinvention, the yield of dibasic acids from the same charge was increasedby about 40%.

The following additional example will serve to further illustrate thehighly efiective results obtained by practicing the present invention.

Example III 6 reached a saponiilcation value of 566 and an acid value of342; that is. an acid/saponiflcation value of 0.6.

The crude oxidation product was subjected to a pyrolysis treatment inthe presence of a catalyst by charging the oxidized hydrocarbon througha pre-heat tube into the tube of a flask containing a silica-aluminacracking catalyst. The vaporized stock passed through the catalyst bedto a condenser and receiver, the distillation being conducted under avacuum of 10-20 mm. absolute pressure. A summarized tabulation of theconditions employed is' as follows:

Analysis of charge:

Acid value 342 Saponification value 566 Acid saponiiication 0.60

Catalytic treating conditions:

Temperature (average) C 310 Contact time (calculated in seconds) 2.6Ratio of volume of charge stock/catalyst/hour 2.4

Analysis of distillate:

Per cent yield of distfllate from charge stock 70 Acid value 404Saponification value 515 Acid/saponification 0.78

' Filtration of the distillate resulted in a 13% yield of dibasic acidcrystals having an acid value of 582 and a saponiflcation value of 560.Vacuum distillation of the filtrate into 2 cuts, and filtration of thecuts, yielded 3.3% of dibasic acid crystals of acid value of 539 andSaponification value of 629 and 9% of crystals of acid value of 404 anda saponification value of 515. Redistillation of thenon-crystalline-portions of the two outs yielded an additional 6% ofdibasic acid crystals. Thus, the total yield of dibasic acid crystals,based on the weight of charge stock, was 31.3% which represents a markedimprovement of about 50% in yield over a similar run, under similarconditions except that no catalyst was employed in which only about 20%of dibasic acid crystals were recovered.

Although, as set forth in the foregoing examples, the dibasic acids havebeen recovered from the distillate obtained by the catalytic pyrolysisof the crude oxidized hydrocarbons, it is within the scope of theinvention to include similar treatment for recovery of dibasic acidsfrom other complex acidic mixtures that contain dibasic acids orcertainpotentially acid constituents convertible to dibasic acids. Forexample, it is within the scope of the invention to thus treat theresidual, or bottoms, fractions obtained from the catalytic pyrolytictreatment of the crude oxidized hydrocarbons. Examples of such residualfractions are those such as set forth in Examples I and II as bottomsobtained in the breakdown of the crude oxidized hydrocarbons. Analysisof such residual portions, i. e., the portion that does not vaporize anddistill over, indicates that they are comprised main y of highlyoxygenated compounds and probably polyesters and polylactones averagingaround four saponiflable groups per molecule, and having a substantiallyhigh averawaits jecting such residual materials or fractions thereof toa catalytic pyrolysis treatment in accordance with the presentinvention.

The exact reactions occurring during the catalytic pyrolysis treatmentas embodied herein are not fully known and defy determination since boththe charge material and the product of the treatment contain monoandpolyfunctional compounds whose chemistry is dependent not only onfactors such as chain lengths, but also upon juxtaposition of otheractive groups. However, since the products of the catalytic pyrolysistreatment contain more readily crystallizable and distillable materialsthan the charge subjected to treatment, it would appear that suchoperation results in removal and/or decomposition of substances tendingto inhibit crystallization of dibasic acids, as well as conversion ofcertain potentially acid constituents to dibasic acids.

The dibasic acid products from the catalytic treatment, fractionsthereof, or mixed crystalline dibasic acids separated therefrom areuseful without further treatment as chemical intermediates in thepreparation of plastics and synthetic fibers or plasticizers, and forother purposes. However, individual crystalline dibasic acids may beseparated therefrom and further purified, if desired. Succinic,glutaric, and suberic acids may be isolated by fractionation andrecrystallization procedures, as well as dibasic acids in the carbonatom range of brassylic acid, having an acid value of 463, and dibasicacids in the range of pentadeca'nedioic (C15) having an acid value of420.

The improvement in yield ,and quality of the oxidized hydrocarbonstreated in accordance with this invention is clearly evident bycomparison of acid/saponification ratios of the crude charge stocks withthose of the distillates obtained by catalytic pyrolysis treatment ofsuch stocks. As evidenced by the data set forth hereinbefore, in eachcase, the distillates thus obtained had an acid/saponification valuehigher than the crude charge stock from which they were obtained. Forexample, in Example II, the charge stock had an acid/saponificationratio of 0.63 whereas the distillate from the catalytic pyrolysisthereof had a ratio of 0.78. Similarly, in Example III, the charge stockhad an acid/saponification ratio of 0.6 whereas the distillate of thecatalytic pyrolysis treatment had a ratio of 0.78. The fact that thisratio is materially greater in the case.

of the product than the charge indic'ates'that the product contains morefree carboxyl 'groups than the charge, and hence, that by subjecting thecrude product to the catalytic pyrolysis treatment, certain potentiallyacid components are broken down or converted to free acids along withremoval or decomposition of certain crystallization inhibitingsubstances without causing substantial; if any, decarboxylation, asevidenced by Distillate Acid Catalyst value Saponiilca- Acid/Sapontionvalue ification Silica (SlOa) Alumina (A1105) 10% ZnO on Silica 10%Cobalt on Silica v asses Although, as illustrated hereinbefore, thepresent invention may be satisfactorily practiced with various types ofcracking catalysts, silicacontaining catalysts generally are employed,as

for example, silica, silica-alumina, various metal oxides, e.-g., zincoxide on silica, certain metals, e. g., cobalt on silica, and the like.The catalysts may be suitably employed in various forms, as for example,in the form of pellets, beads, etc. In a preferred embodiment,silica-alumina containing catalysts, such as widely employed forcatalytic cracking of hydrocarbons, are employed as use of suchcompositions appear to provide. effectively high yields of dibasic acidcrystals from charge stocks subjected to treatment in accordance withthis invention.

As set forth hereinbefore, the oxidized hydrocarbons embodied herein forcharge materials to the catalytic pyrolysis treatment havesaponiflcation values of at least 400 and an acid value lower than thesaponification value. The intermediate compounds that inhibitcrystallization of dibasic acids in the charge stock, that is, thecompounds making up the difierence between the acid and saponificationvalues of the charge appear to be complex in structure, and hence, theexact structure thereof is not readily ascertainable. However, analysisthereof shows that the compounds accounting for the difference betweenthe saponification and acid values give lactone and ester values, withthe lactone value generally being substantially greater than the estervalue. Hence, it appears that the carboxyl groups of the greaterproportion of the intermediate compounds are bound by certain linkages,for example, such as are present in lactones. As an illustration, thefollowing is an example of an analysis of an oxidized hydrocarbonfraction, suitable as a charge stock in practicing this invention, alongwith the corresponding analysis of the distillate, obtained in 45%yield, resulting from the, catalytic pyrolysis of the oxidizedhydrocarbon in accordance with the The foregoing data clearlyillustrates not only 76 the material improvement obtained in acid: sa-

poniilcation ratio of the distillate over the charge stock, but also,that the compounds giving a lactone value were preferentially decomposedas evidenced by the material decrease in lactone value. Since compoundshaving their carboxylic groups bound, such as by lactone linkages, aregenerally understood to be more heat stable than corresponding compoundsthereof in which the carboxylic groups are not bound, as in thecorresponding dibasic acids, it is apparent that practice of the presentinvention in subjecting the charge stock embodied herein to catalyticpyrolysis with preferential decom osit on of the intermediate compounds,iving lactone values. in

mixture thereof with dibasic acids, provides a novel and unexpectedresult.

Although the present invention has been described in conjunction withcertain preferred embodiments thereof. those skilled in the art willreadily recognize that variations and modifications can be made. Suchvariations and modiflcations are to be considered to be within thepurview of the specification and the scope of the appended claims.

I claim:

1. A method for improving the yield of crysta line polybasic acids froma non-crystalline polybasic acid-con aining-oxidized mixture obtained byliquid phase oxidation of a predominantly parafiinic hydrocarbon mixturewith a free oxygen-containing gas, said oxidized mixture having asaponiflcation value of at least about 400 and an acid valuesubstantially less than the saponification value and furthercharacterized by containing, as components accounting for a substantialportion of the difference between the aforesaid acid and saponiflcationvalues. oxygenated compounds inhibiting crystallization of polybasicacids in said oxidized mixture which comprises subjecting said oxidizedmixture at a distillation temperature therefor to contact with acatalyst comprising a metal oxide from the group consisting of aluminaand silica and mixtures thereof for a period of time suflicient todecompose a substantial portion of said crystallization-inhibitingcompounds without effecting substantial decomposition of the polybasicacids in said mixture to provide a distillate containing a substantialamount of polybasic acids in crystalline form.

2. A method, as defined in claim 1, wherein the oxidized mixture issubiected to contact with the catalvst at a temperature of about 200 C.to about 400 C.

3. A method, as defined in claim 1, wherein the oxidized mixture issubiected to contact with the catalyst at about 200 C. to about 400 C.for about 0.5 to aboutseconds.

4. A method. as defined in claim 1, wherein the crystalline polybasicacids are separated from the distillate.

5. A method for improving the yield of crystalline polybasic acids froma non-crystalline polybasic acid-containing oxidized mixture obtained byliquid phase oxidation of a predominantly paraifinic hydrocarbon mixturewith a free oxygen-containing gas, said oxidized mixture having asaponification value of at least about 400 and an acid valuesubstantially less than the saponification value and furthercharacterized by containing, as components accounting for a substantialportion of the difference between the aforesaid acid and saponiflcationvalues, oxygenated compounds inhibiting crystallization of polybasicacids in said oxidized 75 mixture, which comprises subjecting saidoxidized mixture at a distillation temperature therefor to contact witha catalyst effective at said temperature to decompose saidcrystallization-inhibiting compounds in preference to decomposition ofpolybasic acids in said oxidized mixture to provide a distillatecontaining a sub stantial amount of polybasic acids in crystalline form.

6. A method for improving the yield of crystalline polybasic acids froma non-crystalline polybasic acid-containing-oxldized mixture obtained byliquid phase oxidation of a predominantly parafflnic hydrocarbon mixturewith a free oxygen-containing gas, said oxidized mixture having asaponiflcation value of over 400 and an acid value substantially lessthan the saponification value and further characterized by containing,as components accounting for a substantial portion of the differencebetween the aforesaid acid and saponification values, oxygenatedcompounds inhibiting crystallization of polybasic acids in said oxidizedmixture, which comprises subjecting said oxidized mixture at adistillation temperature therefor to contact with a hydrocarbon crackingcatalyst comprising an oxide of a metal from the group consisting ofaluminum and silicon and mixtures thereof for a period of timesufiicient to decompose a substantial portionof saidcrystallization-inhibiting compounds without afiecting substantialdecomposition of polybasic acids in said mixture to provide a distillatecontaining a substantial amount of polybasic acids.

7. A method, as defined in claim 6, wherein theoxidized mixture issubjected to contact with the catalyst at a temperature of about 200 C.to about 400 C.

8. A method, as defined in claim 6, wherein the oxidized mixture issubjected to contact with the catalyst at a temperature of about 200 C.to about 400 C. for about 0.5 to about 5 seconds.

9. A method for obtaining improved yields of crystalline polybasic acidsfrom a non-crystalline polybasic acid-containing-oxidized mixtureobtained by liquid phase oxidation of a predominantly parafllnichydrocarbon mixture with a free oxygen-containing gas, said oxidizedmixture having a saponification value of more than 400 and an acid valuesubstantially less than the saponiflcation value and furthercharacterized by containing, as components accounting for a substantialportion of the difference between the aforesaid acid and saponificationvalues, oxygenated compounds inhibiting crystallization of thenon-crystalline polybasic acids in said oxidized mixture, whichcomprises subjecting said oxidized mixture at a temperature of about 200to about 400 C. to contact for about 0.5 to about 5 seconds with acatalyst comprising a metal oxide from the group consisting of silicaand alumina and mixtures thereof to provide a distillate containing asubstantial amount of polybasic acids in crystalline form.

10. A method, as defined in claim 0, wherein the crystalline polybasicacids are separated from the distillate.

11. A method for obtaining improved yields of crystalline polybasicacids from a non-crystalline polybasic acid-containing-oxidized mixtureobtained by liquid phase oxidation of a predominantly paraflinichydrocarbon mixture with a free oxygen-containing gas, said oxidizedmixture having a saponiflcation value of more than about 400 and an acidvalue substantially less than the saponiflcation value and further char-11 acterized by containing, as components accounting for a substantialportion of the difference between the aforesaid acid and saponlflcatlonvalues, oxygenated compounds inhibiting crystallization of thenon-crystalline poiybasi-c acids in said oxidized mixture, whichcomprises subjecting said oxidized mixture at a temperature of about 200to about 400 C. to contact for about 0.5 to about 5 seconds with acatalyst effective, under said temperature and time conditions, todecompose said crystallization-inhibiting compounds in preference todecomposition of polybasic acids in said oxidized mixture to provide adistillate containing a substantial amount of polybasie acids incrystalline form.

CARL N. ZELLNER.

12 REFERENCES CITED The following references are of record in the fileof this patent:

6 UNITED STATES PATENTS Number Name Date 1,940,400 Dietrich Dec. 19,1933 1,965,961 Luther et a1 July 10, 1934 10 2,055,095 Beller et al. (B)Sept. 22, 1936 2,059,201 Beller et al. (A) Nov. 3, 1936 2,059,232 HarderNov. 3, 1936 FOREIGN PATENTS Number Country Date 433,780 Great BritainAug. 14, 1935

